WW1 Planes
An encyclopediae of 1914-18 aircraft types

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Junkers Flugzeug und Motorenwerke AG

Junkers Junkers Flugzeug- und Motorenwerke AG (called JCO or JKO in World War I), simplified as Junkers, was a major German aircraft and engine manufacturer better known for its WW2 products like the legendary Ju-87 "Stuka" and Ju-88 dive bombers or the transport plane Ju-52 among others, despite the fact that Junkers himself was not pro-Nazi and was removed from the company in 1934. But the company started in the Great war, producing some of the most innovative airplanes in Dessau, Germany. Founded in 1895 by Hugo Junkers, which had experience only so far in making boilers and radiators, the company pioneered the all-metal aircraft, in 1915. The serie started with this revolutionary J1 and went up to the J11 floatplane and other projects that were not ready on time during the war. Converting into civilian planes saved the company, which could go on staying on the edge of technology, until after 1933 the times were right again for a gradual return to military production. And the company went on its innovative path with world's first heavy jet bomber, four-engine, with inverted swept-wing, the Ju-287.

Junkers J-1
Junkers-1, the world's first all-metal fighter

Of course the model that launched it all was the J-1, first all-metal fighter (and plane by the way). It was modelled after a monoplane, because the biplane structure was judged too weak then to handle the weight, and a single prototype flew on 12 December 1915 and was further tested in 1916, giving birth to better models. It was Pioneered by the aeronautical designer Hugo Junkers, constructed and flown only 12 years after the Wright Brothers, which gave a sense of the speed of aircraft development made in between. Junkers would remain the only manufacturer of such planes until the end of the war, worldwide. Hugo Junkers was not new to metal working. His skills were developed from the calorimeter and various internal combustion engines parts he designed and licenced. However he was introduced to the idea of planes by Hans Reissner, a colleague and fellow professor at the Technische Hochschule in Aachen, present at his thermodynamic training course. He seeked the assistance of the latter to make fly an early monoplane aircraft (which was not a success), and five years later, in 1913, the two collaborated on an all-metal canard design, which he named the Ente ("Duck"). Still based on Reissner design, Junkers manufactured the flying surfaces and radiator. But Hugo spent a great deal of time figuring out problems of airframe design, and a way to get rid of bracing. He eventually patented a fully cantilevered thick aerofoil tailless aircraft, or flying wing. He was also granted in 1910 the construction of a wind tunnel at his research facilities in Aachen, where the R&D facilities were located. He set-up his own research institute and devoted his time designing and develop a series of fully cantilevered all-metal monoplanes, and from 1914, models with potential military value.

Junkers J-1, back view
Junkers-1, back view. This prototype was sluggish enough to be compared to a donkey.

Since teamwork is often the base for success, Junkers was able to transform his institute into a successful business thanks to engineers Otto Reuter, Otto Mader (Forschungsanstalt - heads of the R&D institute) and Hans Steudel, head of Junkers' structural materials section. His work on Reissner's Ente convinced him that the only way to get rid of external bracing (which produce drag), was to create an all-metal structure. Although duralumin, invented by Alfred Wilm six years earlier in Germany was prone to flaking, so Junkers preferred proven but heavier electrical steel, and only in 8 June 1915 he started procuring himself with the necessary tooling. He soon started working on a "technology demonstrator", the J-1, a private-venture research aircraft, never commissioned. Using a cantilever wing and all-metal structure elements, the J1 was of a very clean design, with perfect proportions in relation to the power, a reliable 90 kW (120 hp) Mercedes D.II six-cylinder liquid-cooled inline engine, with a profiled cowling, combined to an advanced engine radiator layout (ventral). Structurally reinforced by corrugated sheets, it used an all-metal stressed-skin construction, the world's first plane to do so. The tail had mobile fins, and the angle of incidence of the stabilizer could be set from the ground. The internal structure used tubes, I-beam sections and stip-steel angle stock, while there was some limited external bracing, on horizontal stabilizers and the undercarriage. The steel panels with span-wise corrugations he used in particular on the wings was reused in the late 1930s in planes such as the Boeing B-17.

Junkers J-2 side view
Junkers J-2, side view. This pre-production model gained some power an a modern undercarriage, but did not convinced the Idflieg. (src 1000aircraftphotos.com)

Even before its first flight, the IdFlieg, Inspektorat der Fliegertruppen was quite interested, and ordered static load tests in the end of 1915 and later engine thrust tests in December at Fliegerersatzabteilung 1 (FEA 1) airfield in Döberitz near Berlin. There was a first hop by Leutnant Theodor Mallinckrodt on 12 December 1915 and then from 18 January 1916, Gefreiter (Private) Paul Arnold multiplied fly tests at various altitudes and speed; It was unfavorably compared to the Rumpler C.I, being slower in straight line and more so in climbing rate. In addition, several issues on the ground were also spotted. But specialists such as Anthony Fokker all praised the effort. Only a better engine was needed at that point. This was for the next steps of the Company... The J-2 passed all tests wth brio and was declined for production as the E.I (Junkers Eindecker I). But "production" was limited to six pre-production models. It was still a brilliant concept, innovating with "unitized" the forward fuselage structure, integrating the wing roots, engine mount and cockpit, also a world's first.

The J.2 was a clear-cut improvement on performance and handling, but in the summer of 1916 Hugo Junkers himself realized that the use of sheet electrical steel was not practical for aircraft production. In fact the company was still stuck in ongoing experimentations, compounded by substandard climbing performance and a fatal crash that did not compensated by the theoretical advantages of low-drag because of thr absence of external bracing. As the result the Idflieg eventually retired its support for the program. Despite this lack of support, Junkers already start working in parralel on a much lighter model, the Junkers J-3. This was the first attempt to use duralumin for the airframe construction, a mid-wing with a rotary engine and aluminum tubing fuselage. In this corrugated sheet duralumin covered the wing structures reinforced by "bare" tubular framing for the fuselage. This was an unfinished engineering exercise abandoned at the end of 1916. The J.4 was back to the biplane formula and was delclined into the armoured plane J.I (yes, can be confusing, see below). It was followed by a paper project, the Junkers J-5, developed in early 1917 with a cantilever wing, based on the J-4 so using duralumin. It was declined into two prototypes, the J 5I fitted with a Siemens Sh2 or Oberursel UR.II engine unusually behind the cockpit to improve balance and handling, the J 5II with the same engine in front, and J 5III later called Junkers J-6 with a Mercedes D.IIIa and a parasol wing.

Models produced

Junkers J.1
Junkers J.I, the biggest success of the company during WW1

The "Stuka" of WW1 was not a dive bomber, but it was a successful ground attack aircraft, and a frank success by Junkers. After the failure of all-metal fighters, the company worked on the J-4 (factory designation). It was an armored sesquiplane developed as a low-level ground attack, also capable of observation and Army cooperation. To compensate for the weight, both of the structure and armor it was powerful with a Benz Bz.IV, 149 kW (200 hp) and had a lower wing for sustentation, but indeed, only showed oblique struts between the fuselage and lower wings and the upper wing, no intermediary struts. Although costly, this plane armed with a simple observer MG on a flexible mount was well liked by its crew for its ruggedness, but less so for its poor handling, nicknaming it the "furniture van". It weighted indeed 2,140 kg (4,718 lb) and its top speed was 155 km/h (97 mph). It was produced until the end of the war, arriving in time for the spring offensive in May 1918, but Junkers was unable to deliver them at a steady pace and it remained the only mass-produced Junkers plane of the war.

Junkers J.1
Junkers J-7 prototype, from which was derived the serial D.I

Junkers modified its copy on the next Junkers J-8, a private venture which first flew on 17 September 1917 and went through nearly a half-dozen detail changes resulting of the tests. So much so that Junkers felt confident enough to demonstrated it to the Idflieg after its past failure, in early 1918. And it attracted praise, resulting in an order for three more for additional army trials. However, the changes made cumulated to the point of Junkers creating a brand new prototype, the J 9 tested by Idflieg instead of the three J 7s initially ordered. This model was eventually reclassed as a naval fighter and production took place of two batched of 12 at the end of the war. Junkers D.1
Junkers D.I, the sole all-metal operational fighter of WW1

Junkers returned to the fighter after working with duralumin and aluminium to produced at last a workable, light enough, but still all-metal fighter. It proceeded from the J.7

Models listing in detail

  • Junkers J 1 - experimental monoplane 1915 (1)
  • Junkers E.I - monoplane fighter, 1916 (6)
  • Junkers J 3 - abandoned development of J 2
  • Junkers J.I - ground attack, 1917 (227)
  • Junkers J 5 - fighter prototype project (2 variants) 1917
  • Junkers J 6 - fighter prototype parasol project 1917
  • Junkers J 7 - fighter prototype, led to D.I
  • Junkers CL.I - ground attack, 1917 (40)
  • Junkers D.I - fighter, 1917 (41)
  • Junkers CLS.I - seaplane two-seat fighter (3)

Junkers E-I 1916

Prior to this model, the first prototype was nicknamed the Blechesel ("Tin Donkey" or "Sheet Metal Donkey"). This amazing plane made extensive use of metal in and around its structure and surfaces instead of wood and canvas. It should be noted however that many manufacturers created a tubular metal box that was covered either with plywood and canvas.

Junkers J-2
Junkers J-2

Junkers E-I Specs
Dimensions: 7.43 x 11.70 x 3.13 m (24 ft 4½ in, 38 ft 4⅔ in, 10 ft 3¼ in)
Weight: 920 kg (2,028 lb) to 1,165 kg (2,568 lb) gross
Powerplant: Mercedes D.III water-cooled engine, 119 kW (160 hp), 200 km/h (124 mph)
Range: 615 km (382 miles), Service ceiling: 4500 m (14,760 ft)
Armament: 7.92 mm (.312 in) lMG 08/15 machine gun

Junkers J.I 1917

The most produced Junkers plane of the era was defined not as a fighter, a personal Hugo Junkers obsession marked by a long line of prototypes, but still quite innovative. As a ground attack, armoured plane, it had a single-unit steel "bathtub", starting after the propeller up the rear crew position. Not it was armoured but structured the main fuselage structure and engine mounting in a "monocorps" fashion. The armour plates were 5 mm (0.20 in) thick, adding a whooping 470 kgs (1,040 lb) to protect the crew, radio and fuel tank. To lift the lot, the J.I was fitted with a 35.89 m2 (386.3 sq ft) upper wing (with ailerons), and half for the lower wing 13.68 m2 (147.3 sq ft), in a pure sesquiplane configuration. And also innovative were the flight control surfaces connected by push-rods and bellcranks rather than steel cables, suited here as less likely to be cut by ground fire. Gravity-serving 120 litres (32 US gal) tanks and the planes could be disassembled easily into wings, fuselage, undercarriage, and tail for easy transport and maintenance. The planes could be assembled in 4-6 hours by a small team but great care had to be taken of the thin aluminum skin.

J.I blueprint
Blueprint of the Junkers J.I

All in all, the J.I made an excellent job after its introduction in August 1918, and was well liked by its crews despite its nickname of "furniture van" as it lacked agility and was heavy on commands. They saw action on the Western Front, in full force during the German Spring Offensive of 1918. Improvements in the field were made, two downward-firing machine guns for ground attacks. J.I excelled at army co-operation and low-level reconnaissance, dropping ammunition and rations on isolated outposts also, all under enemy fire. Only one J.I was reported down by a ground-base fire a French AA machine gun firing armour-piercing rounds. In fact more were lost because of landing accidents and other factors. But in the end, much more J.Is could have been operational if that was not for the slow rate of delivery caused by a lack of organization. Production ceased in January 1919. Only one survived, now at the Canada Aviation and Space Museum, partially cutout to see construction details but also in dire need of repairs...
Junkers J.I Specs
Dimensions: 9.1 x 16.00 x 3.4m (29 ft 10 in x52 ft 6 in x11 ft 2 in) Weight: 1,766 kg (3,893 lb) to 2,140 kg (4,718 lb) Powerplant: Benz Bz.IV, 149 kW (200 hp) 155 km/h range: 310 km 4,000 m ceiling Armament: Rearward trainable 7.92 mm (.312 in) Parabellum MG14 MG

Junkers D.I 1918

Basically the D.I was based non the new J-3, which structurally still possessed the advantages of the duralumin-based J-3, but with a lengthened fuselage, extended wingspan and better engine. The Idflieg eventually ordered it as the Junkers D.I, ordering a preserie called J.9/II which underwent further evaluations. Indeed it still lacked the agility suited to a proper front-line fighter, but was was still judged fit for a naval fighter. A first batch of 12 was ordered. These were supplied to a naval unit by September 1918, and sent the Eastern Front after the Armistice. While a single survivor could be seen at the Musée de l'Air et de l'Espace in France, there are replicas, notably in Germany.

The D.I now exhibited at the Musée de l'Air et de l'Espace, Le Bourget, France

Junkers D.I Specs
Dimensions: 7.25 x 9.00 x 2.60 m (23 ft 9.4 in x 29 ft 6.3 in x 8 ft 6 in)
Weight: 654 kg (1,438 lb) to 834 kg (1,834 lb)
Powerplant: BMW IIIa water-cooled 6-cylinder inline, 138 kW (185 hp)
Performance: Top speed: 176 km/h (109 mph), 1.5h, 6,000 m (19,700 ft) 3.5 m/s (683 ft/min) Armament: 2 fixed, forward-firing Spandau machine guns.

Junkers CL.I 1918

Junkers CL.I
The CL.I in 1918

The Junkers CL.I was designed as a ground-attack aircraft, based on the factory-designated J 8 another Hugo Junkers all-metal monoplane, despite the Idflieg ordering a biplane whch ended as the J 4, entering competition for a ground-attack aircraft. The J 8 was based on the J 7 fighter with a longer fuselage for a tail gunner, and larger wings to cope with the added weight. The J 7 first flew in late 1917, followed by three more prototypes. They were shown to the Idflieg which at first ordered the type, but doubting Junkers abilities to mass-manufacture it, considered asking Linke-Hoffmann for licenced production. Junkers was chosen in the end under a joint venture with Fokker, which produced the modified J 10. As said above, Anthony Fokker was quite impressed by the design and saw this as an opportunity to study the concept first-hand. This plane was all-metal, with a tubular and framed structure skinned with thin corrugated duralumin sheets. In all, 47 were delivered before the Armistice. The CL.I was also declined as a floatplane (Only three) designated CLS.I (or J 11). Two CL.Is were converted as airliners with a rear cockpit enclosed. This was the start of a successful civilian serie which culminated with the mass-built Junkers 52, the famous "Aunt Ju".

Junkers J11
The naval variant J-11 or CLS.I in 1918

By the end of the war however, only a few planes had reached the front. Some ended being used by the Freikorps in 1919 against the Bolsheviks in Finland and the Baltic States while others served as courier or passenger planes. The latter were partially rebuilt with an enclosed cabin and flew regularly in March 1919 between Weimar and Dessau. Considerations were made for the Junkers J 12, later declined into the succesful Junkers F 13, one of the most modern airliner at that time.
Junkers J.I Specs
Dimensions: 7.90 x 12.04 x 2.65 m (25 ft 11 in x39 ft 6 in x8 ft 8¼ in)
Weight: 710 kg (1,562 lb), 1,050 kg (2,310 lb)
Powerplant: Mercedes D.IIIa, 134 kW (180 hp), 161 km/h, 2h, ceiling 6,000m
Armament: two fixed, forward-firing machine guns, one trainable, rearward-firing machine gun

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